Electrochemical cell and method of making the same

ABSTRACT

A secondary cell comprising a positive cathode electrode of capacity P (mAh) in communication with a liquid or gel electrolyte; an negative anode electrode of capacity N (mAh) in communication with the electrolyte; and a separator permeable to at least one mobile species which is redox-active at least one of the anode and the cathode; designed and constructed such that the anode capacity N is smaller than that of the cathode capacity P, hence N/P&lt;0.9.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of co-pending U.S.provisional patent application Ser. No. 62/091,413, filed Dec. 12, 2014,which application is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to electrochemical cells in general andparticularly to secondary electrochemical cells.

BACKGROUND OF THE INVENTION

Rechargeable or secondary electrochemical storage devices or batterieshave wide-ranging applications and development of improved batteryperformance is a long-standing goal. Maximizing the volumetric orgravimetric energy density (i.e. minimizing the cell volume or mass) isan important and closely tracked performance metric. Rechargeableelectrochemical cells such as Li-ion and NiMH use an electrochemicallyactive, non-metallic, insertion material at the negative electrode oranode. However, many electrochemical storage systems involve the use ofan electrochemically active metal at the anode. Commercial examplesinclude Pb-acid, Na—NiCl₂ (ZEBRA), Li metal polymer and Ag—Zn, but manyother examples have been explored in the laboratory setting includingLi—S, non-aqueous Na, and Mg.

In general, in all closed system or sealed container liquid-based cells,the cell is designed such that the capacity of the anode exceeds thecapacity of the cathode.

For example in an Mg cell (Aurbach, D. et. al., Prototype systems forrechargeable magnesium batteries, Nature 407(2000), 724-727) thenegative electrode is typically a metallic Mg foil or ribbon on theorder of at least 100 μm thick, or 38 mAh/cm²; containing significantexcess capacity relative to the cathode which is typically constructedat <5 mAh/cm2. Calculating the N/P ratio of these cells, where N and Pare the areal electrochemical capacity of the negative and positiveelectrodes (measured in mAh/cm2), the Mg cells reported in theliterature have N/P typically>10 and frequently>30. For further examplein a Zn cell the negative electrode is typically a Zn metal foil orblock. In still a further example in a Pb-acid cell the anode comprisesa large block of Pb, always in significant excess capacity relative tothe cathode.

Another report is Zheng, Y. et. al., Magnesium cobalt silicate materialsfor reversible magnesium ion storage, Electrochemica Acta, 66(2012),75-81, which discloses a Magnesium battery having a solid Mg metal foilas the anode. The battery is built in the fully discharged state and hasa thick Mg metal foil as the anode, giving an anode excess N/P>1.

In yet another report Liu, B. et. al., Rechargeable Mg-Ion BatteriesBased on WSe₂ Nanowire Cathodes, ACS Nano, 7(2013), 8051-80587, whichdiscloses a Magnesium battery having a solid Mg metal foil as the anode.The battery is built in the fully charged state and has a thick Mg metalfoil as the anode, giving an anode excess N/P>1.

Two classes of closed system Li cells seem especially relevant for thepresent discussion. In a standard Li-ion cell, Li ions are intercalatedinto, or shuttled between, both the cathode and anode. The anode maytypically be graphite, although a range of other anode materials such assilicon, germanium, tin, aluminum, and alloys thereof are also wellknown. In addition, low voltage intercalation hosts, such as lithiumtitanium oxide (Li₄Ti₅O₁₂ or “LTO”), and conversion materials, such aslow voltage oxides, may be used as an anode. In all these cases it iswell known in the art that it is necessary to design a cell with morereversible capacity at the anode than at the cathode. This is to ensurethat during as-rated charging operation (i.e. transfer of lithium andelectrons from cathode to anode at a designated rate) the anode mayalways accept more lithium than is removed from the cathode.Excess-anode devices constructed in this manner minimize the risk ofplating lithium metal during charging which is widely believed to bedetrimental to cell cycle life and safety. Thus lithium-ion cells aredesigned with an excess of reversible capacity on the negativeelectrode, typically denoted as an N/P ratio of >1. The required excessof negative electrode varies depending on the selected anode material,but may typically lie in the range 20-40% (for graphite) to 10% (forLTO). Thus in a lithium-ion battery it is well known that an N/P ratio>1and general N/P>1.1 is required for good operation of the device.

In a lithium metal cell with a liquid or gel electrolyte, the anode ischosen to be a metal foil of lithium or a metallic alloy of Li such asLiAl, (a range of such anodes are well known). Examples of such cellchemistries include lithium-sulfur cells (Sion, Oxis),lithium-molybdenum disulfide (Moli) and lithium-vanadium oxide (Avistor,Valence, Batscap, Bollore, NTT). However lithium metal anodes are knownto be highly reactive, which on cycling continuously generate highsurface area lithium and decomposition products. The generation of highsurface area metallic lithium and decomposition products lowers theonset of thermal instability leading to significant and well documentedsafety hazards. Additionally, metallic lithium anodes are known torapidly lose accessible capacity through the formation of finely dividedand electrically isolated regions of metallic lithium. Because of thereactivity of lithium, such lithium metal cells with liquid electrolyteare designed with a very large N/P ratio. The N/P ratio in a lithiummetal cell is typically around 10, but in cases where the cell volume isminimized N/P may be around 4 (K. Brandt Solid State Ionics 69, (1994)173-183 and Electrically Rechargeable Metal-air Batteries Compared toAdvanced Lithium-ion Batteries, presented by Jeff Dahn at IBM AlmadenInstitute, 2009). Thus in any lithium metal cell having a liquidelectrolyte, it is well known that an N/P ratio>>1 and in general N/P>4is required for good operation of the device (i.e., useful cycle lifeand energy density).

Similar arguments to the forgoing also apply to open-system cells, suchas Zn-air and Li-air and again the cells are designed with a metal anodethat has much larger capacity than the capacity of the cathodeelectrode. While such open-system cells utilize air as an activematerial, the capacity of the cathode electrode (P) is well defined andlimited to a finite value. Therefore in such cells N/P is again designedto be >1.

An exception to the N/P>1 rule would be a solid-electrolytelithium-metal cell such as that reported in U.S. Pat. No. 6,168,884 B1issued Jan. 2, 2001 to Neudecker et al., where it is generally knownthat the solid electrolyte has negligible reaction with the lithiummetal anode, so that a cell may be designed which has an N/P ratio<1.Similar cells have subsequently been reported by numerous authors. Forexample, in Neudecker, a cell is shown having no lithium metal in thefully discharged state. Because the reaction with a solid electrolyte isnegligible, the Neudecker all-solid cell can be cycled reversibly manytimes despite having an N/P ratio<1. However, the cell reported byNeudecker suffers from a prohibitively low electrode loading, generallyless than 0.1 mAh/cm2, required to meet a practical rate capability.

In a similar fashion to Neudecker, other solid-electrolyte cells such asthose described in U.S. Pat. No. 6,402,795 issued Jun. 11, 2002 to Chuet al. use a solid electrolyte barrier layer, also referred to as apassivation layer in conjunction with a liquid electrolyte. The barrierlayer, deliberately coated onto the negative electrode prior to cellassembly, is required to prevent spontaneous and continued reaction ofthe anode material with the liquid electrolyte. However, allsolid-electrolyte cells as well as hybrid barrier layer with liquidelectrolyte cells suffer from major disadvantages in terms ofmanufacturability and rate performance.

Another report is U.S. Pat. No. 5,314,765, Protective lithium ionconducting ceramic coating for lithium metal anodes and associatemethod, issued May 24, 1994 to Bates, which is said to disclose abattery structure including a cathode, a lithium metal anode and anelectrolyte disposed between the lithium anode and the cathode utilizesa thin-film layer of lithium phosphorus oxynitride overlying so as tocoat the lithium anode and thereby separate the lithium anode from theelectrolyte. If desired, a preliminary layer of lithium nitride may becoated upon the lithium anode before the lithium phosphorous oxynitrideis, in turn, coated upon the lithium anode so that the separation of theanode and the electrolyte is further enhanced. By coating the lithiumanode with this material lay-up, the life of the battery is lengthenedand the performance of the battery is enhanced.

In summary, electrochemical systems that contain liquid or gelelectrolyte, and not exclusively solid electrolyte, are designed eitherwith an intercalation anode having an N/P ratio>1 and typically>1.2, orwith a pure metal anode having an N/P ratio>1 and typically>4. Thisarises from a belief that plated metal has a poorly controlledmorphology or undergoes spontaneous chemical reactions with electrolytecomponents and therefore it is advantageous to either have a large metalexcess in order to counteract these processes, or to avoid plating metalaltogether as for intercalation systems.

In a recent report “Electrically Rechargeable Metal-air BatteriesCompared to Advanced Lithium-ion Batteries”, presented at IBM AlmadenInstitute, 2009 by Jeff Dahn, NSERC/3M Canada Industrial Research Chair,Depts. of Physics and Chemistry Dalhousie University: Canada, whichteaches practitioners not to use metallic Lithium in rechargeable cells.Additionally it is said to teach that excess lithium, or N/P>1, is arequirement for electrochemical cells utilizing a metal lithium anode.Specifically N/P=4 is required for useful cycle life.

An additional report is K. Brandt, Solid State Ionics 69, (1994)173-183, which teaches that rechargeable Li batteries in general requireN/P>1 for electrochemical cells.

In yet another report is Harry, Hallinan, Parkinson, MacDowell, andBalsara, Detection of subsurface structures underneath dendrites formedon cycled lithium metal electrodes, Nature Materials 2013, 13, 69-73which is said to disclose that during the early stage of dendritedevelopment, the bulk of the dendritic structure lies within the metalelectrode, underneath the polymer/electrode interface. Furthermore, theyobserved crystalline impurities, present in the uncycled lithium anodes,at the base of the subsurface dendritic structures. The portion of thedendrite protruding into the electrolyte increases on cycling until itspans the electrolyte thickness, causing a short circuit. Contrary toconventional wisdom, it seems that preventing dendrite formation inpolymer electrolytes depends on controlling the formation of subsurfacestructures in the lithium electrode present prior to cell assembly.

Yet another report is Vaughey et al., Lithium Metal Anodes, Annual MeritReview, DOE Vehicle Technologies Program, Washington, D.C., May 19,2009, which is said to teach, inter alia, that cycled lithium metalanodes have a complex morphology that lies at the heart of the lifetimeproblems.

Another report is Mikhaylik, Protection of Li Anodes Using Dual PhaseElectrolytes (Sion Power, DoE EERE report May 10, 2011), which is saidto teach the protection of Li anode with dual phase electrolyteeliminated thermal runaway for 50% of the 0.25 Ah rechargeable Li—Scells tested at end of life.

Yet another report is Park, M. S., et. al. A highly reversible lithiummetal anode. Nature Scientific Reports, 4, (2014), 3815, which is saidto disclose a novel electrolyte system that is relatively stable againstlithium metal and mitigates dendritic growth. A significant basis forthe paper is a cell model in which N/P is 1.1 and 3 (i.e., N/P>1) forlithium ion and lithium metal cells respectively.

Another report is U.S. Pat. No. 6,706,447, Lithium Metal Dispersion InSecondary Battery Anodes, issued Mar. 16, 2004 to Guo et al., which issaid to disclose a secondary battery having a high specific capacity andgood cyclability, and that can be used safely. This document inter aliaexplicitly states the requirement that the amount of metal used in thebattery should be chosen to be less than the amount that can beincorporated into the anode (i.e. N>P)

Yet another report is Li et al., A Review Of Lithium Deposition InLithium-Ion And Lithium Metal Secondary Batteries, Journal of PowerSources 254 (2014) 168-182, which is said to disclose major aspectsrelated to lithium deposition in lithium-ion and lithium metal secondarybatteries are reviewed. For lithium-ion batteries with carbonaceousanode, lithium deposition may occur under harsh charging conditions suchas overcharging or charging at low temperatures. The authors state thatmetal deposition is always disadvantageous, and that the solutionincludes ensuring that the battery design has a sufficiently largeexcess of anode or N/P>1.

Another report is U.S. Pat. No. 6,258,478 B1, Electrode Assembly HavingA Reliable Capacity Ratio Between Negative And Positive Active MaterialsAnd Battery Having The Same, issued Jul. 10, 2001 to Kim, which is saidto disclose a roll electrode assembly used in a secondary batteryincludes a positive electrode applied with a positive active material, anegative electrode applied with a negative active material, and aseparator disposed between said positive and negative electrodes. Athickness of the positive or negative active materials applied onopposite sides of positive or negative substrates of the positive ornegative electrodes are different from each other such that the capacityratio between the positive and negative electrodes (N/P) can bemaintained above 1.

Yet another report is U.S. Pat. No. 5,422,203, Disposing A PreparedElectrolyte Between The Electrodes, The Nonaqueous ElectrolyteComprising Of Lithium Tetrafluoroborate, Lithium Hexafluorophosphate,Dimethyl Carbonate And Ethylene Carbonate, issued Jun. 6 1995 toGuyomard et al., which is said to disclose that irreversible loss oflithium during the initial discharge cycle of secondary batteries withcarbon intercalation electrodes is substantially reduced by employing asthe cell electrolyte a non-aqueous solution of LiPF₆ in a mixture ofdimethylcarbonate and ethylene carbonate. By this means, in a secondarybattery cell comprising, for example, a Li_(1+x) Mn₂O₄ positiveelectrode and a graphite negative electrode, up to about 90% of thetheoretical level of lithium can be reversibly cycled at anexceptionally high rate of about C/1 (complete discharge in one hour)

In yet another report on non-aqueous electrolyte batteries with anegative electrode comprising lithium titanate (LTO), U.S. Pat. No.7,883,797, issued Feb. 8, 2011 to Kishi et al. states “[a] non-aqueouselectrolyte battery . . . has a positive electrode having a dischargecapacity of 1.05 or more times that of a negative electrode thereof”.However, Kishi et al. explicitly recite at column 4, lines 52-60: “Thedischarge capacity of the aforementioned positive electrode ispreferably 1.10 or less times that of the aforementioned negativeelectrode to prevent the extreme drop of the capacity of the entirebattery and the potential of the negative electrode. In particular, thedischarge capacity of the aforementioned positive electrode is morepreferably from 1.05 to 1.07 times that of the aforementioned negativeelectrode to prevent the deterioration of the positive active materialat a temperature as high as 60° C. or more.” The inverse of a ratio(i.e., the N/P ratio) of 1.10 to 1 is a ratio of 1/1.10=0.91.

Another report is Gallagher, K. and Nelson P. Manufacturing Costs ofBatteries for Electric Vehicles. In Lithium-Ion Batteries: Advances andApplications, Pistoia, G. Ed.; Elsevier Science & Technology Book, 2014;p 103, which teaches the negative electrode thickness is determined byits specific reversible capacity and the designed excess capacity toprevent lithium plating during charging. The report teaches a ratio of1.25 negative to positive reversible capacity ratio (N/P ratio) forcells with graphite negative electrodes. Lithium titanium oxide (LTO)negative electrode-based cells are designed at a 1.1 N/P ratio becauseof the minimal possibility of lithium metal deposition.

There is a need for improved secondary electrochemical storage devicesand maximizing the volumetric or gravimetric energy density of saiddevices remains a clear design goal.

SUMMARY OF THE INVENTION

The present invention is based on three novel and very surprisingobservations. First, the surface roughness obtained by stripping a metalanode is larger than that obtained by plating the same metal onto asubstrate of another kind. Second, that by appropriate choice of platingconditions it is possible to obtain useful cycle life from a metal anodeplated in-situ, for the first time, onto a substrate of another kind andsubsequently cycled reversibly. Third, that the first two observationsare valid for both Mg and Li.

According to one aspect, the invention features a secondary cellcomprising a cathode electrode capable of a capacity of P mAh incommunication with a liquid or gel electrolyte; an anode electrodecapable of a capacity of N mAh in communication with the electrolyte;and a separator permeable to at least one mobile species which isredox-active at least one of the anode and the cathode; designed andconstructed such that the anode capacity N is smaller than that of thecathode capacity P, hence N/P<0.9.

According to another aspect, the invention features a secondary cellcomprising a cathode electrode capable of a capacity of P mAh incommunication with the electrolyte; an anode electrode capable of acapacity of N mAh in communication with the electrolyte; and separatorpermeable to at least one mobile species which is redox-active at leastone of the anode and the cathode, characterized in that the anodecapacity N is about equal to that of the cathode capacity P.

According to another aspect, the invention features a secondary cellcomprising an electrode capacity ratio of N/P≦0.9 and a liquid or gelelectrolyte in direct interface with the anode active material.

In another embodiment, the invention comprises a secondary cell whereinnegligible redox active material is contained at the anode when the cellis nominally at 100% depth-of-discharge, therefore N/P is about equal to0.

In another embodiment the cell may be manufactured in thefully-discharged state and charged subsequent to sealing of the cell, sothat the plating metal is deposited in-situ within the cell and withoutexposure to the environment and resulting adverse reactions.

In one embodiment the anode may be magnesium metal, said magnesium beingfully incorporated into the discharged cathode when the cell is built,so that the metal anode forms only during the first charge of the cell.A benefit of this is that the resulting metal morphology may lackfeatures arising from undesired reactions with ambient atmosphere.

In one embodiment the anode may be lithium metal, said lithium beingfully incorporated into the discharged cathode electrode when the cellis built, so that the lithium metal anode forms only during the firstcharge of the cell. A benefit of this is that the resulting metalmorphology may lack features arising from undesired reactions withambient atmosphere.

In another embodiment, the invention features a secondary cellcomprising a gel electrolyte in direct interface with the anodeelectrode.

In another embodiment, the liquid or gel electrolyte contains a saltanion comprising at least one of boron, carbon, nitrogen, oxygen,fluorine, aluminum, silicon, phosphorous, sulfur, or chlorine.

In still another embodiment, the secondary cell is configured toenable>99.35% Coulombic efficiency between the electrolyte and negativeelectrode.

In yet another embodiment, the secondary cell is configured as amulti-layered prismatic, or laminate cell, or a wound jelly roll in acylindrical, or flat prismatic.

In a further embodiment, the secondary cell is configured to contain aso-called gate electrode, a third electrode disposed predominantlybetween the anode and cathode electrodes, in addition to the cathodeelectrode and the anode electrode.

According to one aspect, the invention features a rechargeableelectrochemical cell. The rechargeable electrochemical cell comprises anon-aqueous fluid electrolyte; a negative electrode in direct physicalcontact with the non-aqueous fluid electrolyte; a positive electrode indirect physical contact with the non-aqueous fluid electrolyte; anelectronically insulating separator configured to separate the negativeelectrode and the positive electrode; the positive electrode and thenegative electrode configure such that a capacity of the positiveelectrode is strictly greater than a capacity of the negative electrode,

In one embodiment, a ratio of reversible capacity between the positiveelectrode and the negative electrode of the electrochemical cell is suchthat Q(positive electrode)/Q(negative electrode)>1.11.

In another embodiment, the rechargeable electrochemical cell isconfigured to charge to greater than or equal to 4.3 V.

In yet another embodiment, the rechargeable electrochemical cell isconfigured to discharge to −2.5 V.

In still another embodiment, the rechargeable electrochemical cell isconfigured to charge and discharge at ≦10 C-rate of rated capacity ineither continuous or pulse current conditions.

In a further embodiment, the rechargeable electrochemical cell isconfigured to discharge and charge at temperatures in the range of −20°C. and 200° C.

In a further embodiment, the rechargeable electrochemical cell isconfigured to discharge and charge at temperatures in the range of −50°C. and 300° C.

In yet a further embodiment, the rechargeable electrochemical cell isconfigured to charge and discharge with >99.35% Coulombic efficiency.

In an additional embodiment, the rechargeable electrochemical cell isconfigured to provide at least 80% of initial capacity for greater than30 charging and discharging cycles.

In still a further embodiment, the negative electrode is configured toprovide>1000 mAh/cc.

In one embodiment, the negative electrode comprises electrochemicallyactive material amounting to less than 100% of the electrochemicallyactive cathode.

In another embodiment, the non-aqueous fluid electrolyte comprises atleast one active cation selected from the group consisting of Mg ion, Alion, Ca ion, Sr ion, Ba ion, Li ion, Na ion, K ion, Rb ion, Cs ion, andonium.

In another embodiment, the non-aqueous fluid electrolyte comprises acomplex cationic species comprising at least one of Mg ion, Al ion, Caion, Sr ion, Ba ion, Li ion, Na ion, K ion, Rb ion, Cs ion, and onium.

In yet another embodiment, the non-aqueous fluid electrolyte contains asymmetric or asymmetric aluminum-based or boron-based anion.

In yet another embodiment, the non-aqueous fluid electrolyte contains asymmetric or asymmetric four-coordinate aluminum-based or boron-basedanion.

In still another embodiment, the non-aqueous fluid electrolyte comprisesa salt, or combination of salts in a concentration in the range of 0.5 Mto saturated concentration.

In a further embodiment, the non-aqueous fluid electrolyte comprises ananion selected from the group consisting of tetrachloroaluminate,tetrachloroborate, bis(oxalato)aluminate, difluoro-oxalato aluminate,difluoro-oxalato borate, or bis(oxalato)borate, bis(malonato)borate,bis(perfluoropinacolato)borate, tetrafluoroborate, triborate (B₃O₇ ⁵⁻),tetraborate (B₄O₉ ⁶⁻), metaborate (BO₂ ⁻), and combinations thereof.

In yet a further embodiment, the non-aqueous fluid electrolyte comprisesat least one of Mg[BF₂(C₂O₄)]₂, Mg[B(C₂O₄)₂]₂, LiBF₂(C₂O₄), LiB(C₂O₄)₂,NaBF₂(C₂O₄), and NaB(C₂O₄)₂, or combinations thereof.

In an additional embodiment, the rechargeable electrochemical cellconfigured to electroplate Mg or Li and the non-aqueous fluidelectrolyte comprises between 1.0 M and 4.0 M of at least one ofLiBF₂(C₂O₄), LiB(C₂O₄)₂, Mg[BF₂(C₂O₄)]₂, Mg[B(C₂O₄)₂]₂, or combinationsthereof, dissolved in at least one non-aqueous organic solvent.

In one more embodiment, at least one of the negative electrode orpositive electrode comprises a metal, an alloy, or an intermetalliccompound.

In still a further embodiment, at least one of the negative electrode orpositive electrode comprises a material configured to undergo aninsertion reaction, an intercalation, a disproportionation, a conversionreaction, or a combination thereof.

In one embodiment, a pressure perpendicular to the interface of thepositive and negative electrodes is greater than 0.06 MPa.

In another embodiment, the rechargeable electrochemical cell furthercomprises at least one gate electrode having a gate electrode electricalterminal, the gate electrode in communication with the non-aqueous fluidelectrolyte and permeable to at least one mobile species which isredox-active at at least one of the positive electrode and the negativeelectrode, the gate electrode situated between the positive electrodeand the negative electrode.

In yet another embodiment, the rechargeable electrochemical cellcomprises a metal, which is configured to plate onto the negativeelectrode during charging.

In still another embodiment, the metal is selected from the groupconsisting of Mg, Li, and Na.

In one embodiment, a ratio defined by the capacity of the negativeelectrode divided by the capacity of the positive electrode is in arange selected from the ranges of zero to 0.10, zero to 0.20, zero to0.30, zero to 0.40, zero to 0.50, zero to 0.60, zero to 0.70, zero to0.80, zero to 0.85, and zero to 0.90.

In another embodiment, a ratio defined by the capacity of the negativeelectrode divided by the capacity of the positive electrode is in arange selected from the ranges of 0.05 to 0.10, 0.05 to 0.20, 0.05 to0.30, 0.05 to 0.40, 0.05 to 0.50, 0.05 to 0.60, 0.05 to 0.70, 0.05 to0.80, 0.05 to 0.85, and 0.05 to 0.90.

According to another aspect, the invention relates to a rechargeableelectrochemical storage device. The rechargeable electrochemical storagedevice comprises an anode electrode comprising the metal form of theelectro-active species, the rechargeable electrochemical storage deviceconfigured to electroplate metal at the anode electrode, the anodeelectrode comprising less than or equal to 3 mAh/cm² of electro-activematerial in the discharged state.

In one embodiment, a ratio of reversible capacity between the positiveelectrode and the negative electrode of the electrochemical storagedevice is such that Q(positive electrode)/Q(negative electrode)>1.11.

In another embodiment, the rechargeable electrochemical storage deviceis configured to charge to greater than or equal to 4.3 V.

In yet another embodiment, the rechargeable electrochemical storagedevice is configured to discharge to −2.5 V.

In still another embodiment, the rechargeable electrochemical storagedevice is configured to charge and discharge at ≦10 C-rate of ratedcapacity in either continuous or pulse current conditions.

In a further embodiment, the rechargeable electrochemical storage deviceis configured to discharge and charge at temperatures in the range of−20° C. and 200° C.

In a further embodiment, the rechargeable electrochemical storage deviceis configured to discharge and charge at temperatures in the range of−50° C. and 300° C.

In yet a further embodiment, the rechargeable electrochemical storagedevice is configured to charge and discharge with >99.35% Coulombicefficiency.

In an additional embodiment, the rechargeable electrochemical storagedevice is configured to provide at least 80% of initial capacity forgreater than 30 charging and discharging cycles.

In still a further embodiment, the negative electrode is configured toprovide>1000 mAh/cc.

In one embodiment, the negative electrode comprises electrochemicallyactive material amounting to less than 100% of the electrochemicallyactive cathode.

In another embodiment, the non-aqueous fluid electrolyte comprises atleast one active cation selected from the group consisting of Mg ion, Alion, Ca ion, Sr ion, Ba ion, Li ion, Na ion, K ion, Rb ion, Cs ion, andonium.

In another embodiment, the non-aqueous fluid electrolyte comprises acomplex cationic species comprising at least one of Mg ion, Al ion, Caion, Sr ion, Ba ion, Li ion, Na ion, K ion, Rb ion, Cs ion, and onium.

In yet another embodiment, the non-aqueous fluid electrolyte contains asymmetric or asymmetric aluminum-based or boron-based anion.

In yet another embodiment, the non-aqueous fluid electrolyte contains asymmetric or asymmetric four-coordinate aluminum-based or boron-basedanion.

In still another embodiment, the non-aqueous fluid electrolyte comprisesa salt, or combination of salts in a concentration in the range of 0.5 Mto saturated concentration.

In a further embodiment, the non-aqueous fluid electrolyte comprises ananion selected from the group consisting of tetrachloroaluminate,tetrachloroborate, bis(oxalato)aluminate, difluoro-oxalato aluminate,difluoro-oxalato borate, or bis(oxalato)borate, bis(malonato)borate,bis(perfluoropinacolato)borate, tetrafluoroborate, triborate (B₃O₇ ⁵⁻),tetraborate (B₄O₉ ⁶⁻), metaborate (BO₂ ⁻), and combinations thereof.

In yet a further embodiment, the non-aqueous fluid electrolyte comprisesat least one of Mg[BF₂(C₂O₄)]₂, Mg[B(C₂O₄)₂]₂, LiBF₂(C₂O₄), LiB(C₂O₄)₂,NaBF₂(C₂O₄), and NaB(C₂O₄)₂, or combinations thereof.

In an additional embodiment, the rechargeable electrochemical storagedevice configured to electroplate Mg or Li and the non-aqueous fluidelectrolyte comprises between 1.0 M and 4.0 M of at least one ofLiBF₂(C₂O₄), LiB(C₂O₄)₂, Mg[BF₂ (C₂O₄)]₂, Mg[B₂(C₂O₄)₂]₂, orcombinations thereof, dissolved in at least one non-aqueous organicsolvent.

In one more embodiment, at least one of the negative electrode orpositive electrode comprises a metal, an alloy, or an intermetalliccompound.

In still a further embodiment, at least one of the negative electrode orpositive electrode comprises a material configured to undergo aninsertion reaction, an intercalation, a disproportionation, a conversionreaction, or a combination thereof.

In one embodiment, a pressure perpendicular to the interface of thepositive and negative electrodes is greater than 0.06 MPa.

In another embodiment, the rechargeable electrochemical storage devicefurther comprises at least one gate electrode having a gate electrodeelectrical terminal, the gate electrode in communication with thenon-aqueous fluid electrolyte and permeable to at least one mobilespecies which is redox-active at at least one of the positive electrodeand the negative electrode, the gate electrode situated between thepositive electrode and the negative electrode.

In yet another embodiment, the rechargeable electrochemical storagedevice comprises a metal which is configured to plate onto the negativeelectrode during charging.

In still another embodiment, the metal is selected from the groupconsisting of Mg, Li and Na.

In one embodiment, a ratio defined by the capacity of the negativeelectrode divided by the capacity of the positive electrode is in arange selected from the ranges of zero to 0.10, zero to 0.20, zero to0.30, zero to 0.40, zero to 0.50, zero to 0.60, zero to 0.70, zero to0.80, zero to 0.85, and zero to 0.90.

In another embodiment, a ratio defined by the capacity of the negativeelectrode divided by the capacity of the positive electrode is in arange selected from the ranges of 0.05 to 0.10, 0.05 to 0.20, 0.05 to0.30, 0.05 to 0.40, 0.05 to 0.50, 0.05 to 0.60, 0.05 to 0.70, 0.05 to0.80, 0.05 to 0.85, and 0.05 to 0.90.

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent from the following descriptionand from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.

FIG. 1A shows a scanning electron microscopy (SEM) micrograph of amagnesium metal anode partially discharged (i.e., partially stripped)from a magnesium cell after repeated stripping and plating upon the Mgmetal anode.

FIG. 1B is an image taken of an Mg metal anode from a magnesium cellafter repeated stripping and plating upon the Mg metal anode.

FIG. 2A shows a scanning electron microscopy (SEM) micrograph of amagnesium metal anode formed by electroplating Mg onto Pt in a magnesiumcell after repeated stripping and plating of the Mg upon the Pt.

FIG. 2B is an image of the Mg metal electroplated onto the Pt workingelectrode in a magnesium cell after repeated stripping and plating Mgupon the Pt metal substrate.

FIG. 3 shows a typical voltage profile of a cell having N/P ratio<0.9and comprising lithium hexafluorophosphate in ethylene dicarbonate anddimethyl carbonate-based electrolyte and cycling Li metal.

FIG. 4 shows a typical voltage profile of a cell having N/P ratio<0.1 inthe discharged state manganese cobalt oxide-based cathode.

FIG. 5 shows a typical voltage profile of a high capacity transitionmetal oxide cell having N/P ratio<0.9 in the charged state.

FIG. 6 shows a capacity fade plot from a 1.7 Ah multi-layer prismaticcell having an N/P ratio<0.9.

FIG. 7 is a capacity fade plot for lithium nickel manganese cobalt oxidecathode cells containing an N/P ratio<0.9 under a variety of rateconditions.

FIG. 8 shows capacity fade plot for cells containing an N/P ratio<0.9 asa function of Depth-of-Discharge conditions.

FIG. 9 shows capacity fade plot for cells containing an N/P ratio<0.9 asa function of cycle.

DETAILED DESCRIPTION

The invention described herein relates to electrochemical cells ingeneral, and particularly to an electrochemical cell having a chargecapacity of the cathode being greater than or equal to the chargecapacity of its anode. We describe a secondary battery having anon-aqueous liquid or gel electrolyte without a barrier layer over thenegative electrode and having less than or equal to the capacity ofelectrochemically active material at the negative electrode than can beaccommodated in the cathode. A goal of the present invention is toprovide a battery utilizing a liquid electrolyte and having a metalanode electrode with electrochemical capacity N, a cathode with capacityP, and an N/P ratio≦0.9. Such a battery will be shown to providesubstantially higher gravimetric and volumetric energy and power thanprior known secondary cells.

It is desirable that secondary electrochemical storage devices avoid themanufacturability problems, poor rate performance, and inability toentirely prevent dendrites associated with solid electrolytes.Furthermore solid electrolyte cells typically require very low loadingof active material, or low utilization at higher loadings thus limitingthe actual energy (Wh), specific energy (Wh/kg), and energy density(Wh/L) that can be delivered in a cell. It is also desired that thesestorage devices are manufactured without adverse air reactions at theanode. Lastly, it is desired to maximize the energy density of thestorage device, by minimizing the volume and mass of electrochemicallyinactive components.

The design described above is motivated by an effort to surpass theenergy and safety limitations of previous secondary cell designs.However, it would appear that the result observed comes as a surprise toone of ordinary skill in the relevant art because cell designspreviously shown to reversibly electrodeposit metal at or near roomtemperature generally required large excess capacity of the anode inorder to demonstrate useful cycle life. However, in adding metal anodesufficient to achieve useful cycle life the resulting energy density ofthe cell is significantly reduced. Owing to the high purity anduniformity of the electrodeposit formed in the cell design describedherein, commercially significant cycle life and energy can be obtained.The purity of the plated metal also enables the creation of cellscapable of tolerating Coulombic inefficiency in a wide variety ofelectrolytes, containing<1000 ppm H₂O, under various cycling conditions.

Further, the technology disclosed herein will enable the use ofcomposite or metallic electrodes without the need for excess electrodematerial, consequently enabling the energy density of batteries toincrease substantially. A technology that also allows the use ofmetallic electrodes would provide the potential for performanceimprovements in many “next-generation” rechargeable chemistriesincluding, as non-limiting examples, Magnesium metal, Sodium metal, andLithium metal. In addition, a technology that would minimize impuritiesin the electroactive anode material will mitigate failure-modes due toboth the generation of high surface area electrode material anddecomposition products at one or both electrodes resulting in thermalrunaway, and dendritic growths that can lead to a short-circuitelectrical condition. Such an invention would allow for greatly enhancedsafety in high energy secondary cells.

Furthermore a technology enabling excess cathode capacity when utilizingconventional intercalation host electrodes including, but not limited tographite, or alloying, conversion, and disproportionation reactionelectrodes will also enhance the battery capacity and safety. FIG. 1Ashows an SEM of a magnesium anode partially discharged (i.e., partiallystripped) after cycling in a magnesium cell. Prior to cycling, the anodeconsisted of bulk Mg foil rolled to a thickness of ˜50 μm. Due to apresumed reaction between atmosphere and the metal, it is expected thatprior to discharge the foil is coated with a thin passivating film of amixed oxide/hydroxide. Further, it is expected that based upon knownliterature that, despite the passivating layer, this anode will cyclewell and become and remain uniform throughout cycling. First, anypassivating films will be rapidly disrupted during initial strippingoperations. Second, as the electrode cycles, any regions remainingpassivated become mechanically unstable until the surface is essentiallyunpassivated and active everywhere. Third, transport within theelectrolyte will favor stripping from the points closest to thecounter-electrode so that an initially rough surface will quickly smoothand become uniform on stripping. Hence it is expected that after cyclingthe surface will become electrochemically active everywhere (i.e. nopassivating film remaining) and with limited height variations orsurface roughness across the surface.

In sharp contrast to previous reports and the known scientificliterature, the SEM in FIG. 1A shows that the surface of a stripped Mganode is heavily pitted and shows local height variations on a scale ofover 50 microns. Deposited Mg material shown in FIG. 1A, 105, is seen onthe surface. In addition, large areas of the “as-prepared” surface, 110in FIG. 1A, of the polished Mg foil remain clearly visible, with theoriginal polishing marks surviving. X-Ray analysis reveals that this isa consequence of passivation of the Mg surface by regions of a mixedoxide/hydroxide, which remains largely inert in the Mg electrolyte evenas Mg metal is being stripped. When stripping of Mg begins, pitsnucleate at pinholes in this passivating film, and then grow veryrapidly. However rather than expanding to include the entire surface ofmagnesium foil, both the stripping and plating remain localized(concentrated) in unpassivated regions. As a consequence of thisbehavior the surface undergoes continual roughening as the cyclingcontinues (as shown in FIG. 1B), rather than becoming smoother. Becausealmost 50% of the area of the electrode is inactive, the thickness ofmetal deposition in the reduced active surface area required to balancethe counter electrode is over twice that required for an electrode with100% active area. Indeed, atomic force microscopy (AFM) of such surfacesindicates height variations of greater than three times the cycledthickness. This roughness will become a prohibitively large overhead inthe design of any cell that includes such an electrode because a largeexcess of anode will be required to achieve the necessary cycle life forcommercial viability.

Given this very unexpected result, the question arises whether theelectrode roughness arising from starting with a native metal anode isactually larger than the roughness obtained by plating the metal onto anelectrode of another kind. Traditionally, plating roughness andspecifically dendrites have been assumed to be small for Mg cells(Aurbach, D. et. al., Chemical Record, 3, (2003), 61 and, Matsui, M.,Journal of Power Sources, 196 (2011), 7048-7055). However, studies of Mgplating and stripping have generally been measured for Mg plated on aninert current-collector, such as Pt, and subsequently cycled while manypractical devices begin with a foil of the native metal. FIG. 2A depictsSEM of the compact, uniform Mg deposit that forms when plating onto a Ptsubstrate, as opposed to the Mg substrate in FIG. 1A. This contrastsuggests that the presence of microscopic non-uniformities on anostensibly uniform and clean Mg surface dramatically impact the overallsurface morphology of the anode during cycling. This image depicted inFIG. 2B shows a highly uniform, micro-foil-like deposit of Mg can becollected from Pt, which is in sharp contrast to the surface of the Mgin FIG. 1B. It is therefore clear that dramatic changes in plated metalsurface morphology can be expected whether a much purer metal anode isformed during an in-situ plating operation versus forming ex-situ priorto introduction into the electrochemical cell. Further evidence of thisis exhibited in the asymmetry of polarization observed between platingand stripping of Mg metal, which is magnified when plating Mg onto Mgvs. depositing Mg onto a dissimilar conducting substrate such as Pt.Therefore it should be expected that important physical properties ofmetal anode cells, such as surface roughness and area, will be differentfor electrodes formed ex-situ versus in-situ to the assembly of anelectrochemical cell.

This is a critical discovery, since it shows that there are majorbenefits to constructing a cell in which some or all of the anode (inthis case Mg) is plated (formed) after the cell is assembled. However,this would correspond to N/P<0.9, generally believed to be problematic.In the remainder of this disclosure we will show that it is in factpossible to overcome the conventional understanding that an N/P ratio ofless than 0.9 is problematic, and we provide a few (non-limiting)examples for how to accomplish this.

While the evidence described thus far is based on observations ofmagnesium metal as the electroactive anode material, we have nowestablished that our findings are in fact transferable to other metals,for example, lithium. It is widely acknowledged that the electrochemicalcycling of lithium metal is intrinsically inefficient, to such an extentthat excess lithium must be introduced into any secondary lithium metalcell to a degree that N/P is often as large as 10, and reports ofpractical cells achieving useful cycle life require N/P equal to 4 areknown. Therefore, any cell in which lithium makes direct physicalcontact with a liquid electrolyte, a lithium metal anode is used inlarge excess to obtain cycle life of practical value. In addition,recent reports indicate that during the early stage of dendritedevelopment, the bulk of the dendritic structure lies within the Limetal electrode, underneath the electrolyte/electrode interface in closeproximity to crystalline impurities present in the uncycled lithiumanode. This is contrary to conventional wisdom, and conforms to thenon-limiting aspects of this disclosure in that a significant aspect ofperformance depends upon controlling the formation of subsurfacestructures in the lithium electrode present prior to cell assembly.

In contradistinction, we have found it possible to construct a cell with(N/P) of about 0 while simultaneously maintaining cycle life requiredfor practical value.

Example 1

FIG. 3 shows a typical voltage profile of a cell containing N/Pratio<0.9. Upon assembly the cell open circuit potential (˜0.3 V) isgenerally representative of the cathode electrode potential differencefrom that of the anode electrode substrate potential (e.g., Ni, Cu,etc.). Initiating cell charging corresponds to a rapid increase in cellpotential as Li⁺ transfers from the cathode to plate out upon the anodeCu substrate, lowering that negative electrode potential to near −3 Vvs. SHE. The corresponding cell potential jumps to about 3.5 V, andrises monotonically thereafter to charge cutoff at about 3.7 V.Thereafter discharge and charge can occur anywhere within this window asthe anode electrode potential remains low due to the potential of thedecomposition products upon the surface. This cell contains a lithiumiron phosphate cathode assembled vs. a copper negative electrodesubstrate and immersed in a lithium hexafluorophosphate in ethylenedicarbonate and dimethyl carbonate-based electrolyte. All cycling wasconducted at room temperature. The first cycle was conducted at 17 mA/gwhile the subsequent cycling is 34 mA/g.

Example 2

FIG. 4 shows a typical voltage profile of a cell containing an N/Pratio<0.1 in the discharged state. Upon assembly the cell open circuitpotential (˜0.3 V) is generally representative of the cathode electrodepotential difference from that of the anode electrode substratepotential (e.g., Cu). Initiating cell charging corresponds to a rapidincrease in cell potential as Li⁺ transfers from the cathode to plateout upon the anode substrate, lowering that negative electrode potentialto near −3 V vs. SHE. The corresponding cell potential jumps to about3.8 V, and rises monotonically thereafter to charge cutoff at about 4.4V. Thereafter discharge and charge can occur anywhere within this windowas the anode electrode potential remains low due to the potential of thedecomposition products upon the surface. This contains a lithium nickelmanganese cobalt oxide cathode assembled vs. a copper negative electrodesubstrate and immersed in a lithium diflurooxolatoborate in ethylenedicarbonate and dimethyl carbonate-based electrolyte. All cycling wasconducted at room temperature and cycle was conducted at C/5 while thesubsequent cycling is 2 C.

Example 3

FIG. 5 shows a typical voltage profile of a cell having N/P ratio<0.9 inthe charged state. Herein we show the corresponding cell voltage profilefor a cell containing a high capacity transition metal oxide whereinmetal ions electrodeposit onto the negative electrode substrate duringthe initial charging. Thereafter the cell charges and discharges whileplating and stripping the metal deposited from the cathode during theinitial charge. This example shows a high capacity metal anode cell withan average voltage quite similar to that obtained by electrodepositingLi metal as depicted in FIG. 3.

FIG. 6-FIG. 9 show various characteristics of the presently disclosedcells, all constructed in a manner such that the Li metal anode isformed in-situ on the first charge of the cell by plating onto an inertcurrent collector. The data for shown in FIG. 6 through FIG. 9 are forcells cycled at room temperature at a variety of charge and dischargerate combinations of commercial relevance.

Example 4

FIG. 6 shows a typical capacity fade plot for a multi-layer prismaticcell of about 1.7 Ah and N/P ratio<0.9. The plot shows the capacity fadeas a function of the first 100 cycles based upon the normalized specificcapacity of the lithium nickel manganese oxide cathode active material.The high purity and highly uniform metal deposit at the anodeenables>33% capacity retention at cycle 100. The as-assembledconstruction is lithium nickel manganese oxide cathode vs. Cu negativeelectrode substrate, and as in FIG. 3, high purity Li metalelectrodeposits at the negative electrode substrate upon initial charge.The rate of charge and discharge is C/2 and the cycling was conducted atroom temperature.

Example 5

FIG. 7 contains a capacity fade plot for cells containing N/P ratio<0.9under a variety of rate conditions. The plot shows the dischargecapacity fade as a function of the first 50 cycles based upon thenormalized specific capacity of the lithium nickel manganese cobaltoxide cathode active material. The as assembled construction is lithiumnickel manganese cobalt oxide cathode vs. Cu negative electrodesubstrate, and as in FIG. 3, high purity Li metal electrodeposits at thenegative electrode substrate upon initial charge. The cycling wasconducted at room temperature and the C-rates depicted forcharge/discharge are 0.5 C/3 C, 0.5 C/2 C, 1 C/3 C, 1 C/4 C (depicted asblack to light grey trends). The capacity fade is generally invariant asa function of rate of charge and discharge.

Example 6

FIG. 8 contains a capacity fade plot for cells containing N/P ratio<0.9comparing cells with 100% depth-of-discharge as compared to 87%depth-of-discharge. Significantly, the capacity loss for all cells inFIG. 8 is less than 10% over the number of cycles shown. The plot showsthat the capacity fade can be suppressed by cycling at <100% depth ofdischarge. In this example, the negative electrode was the embodiment ofthe location in which the residing Li was stored. That is 100% of thecell's electroactive Li was electrodeposited at the anode during firstcharge after assembly and subsequently only 87% of that Li was cycled.The as assembled construction is lithium nickel manganese oxide cathodevs. Cu negative electrode substrate. The cycling was conducted at roomtemperature and the C-rates of formation were C/5 while subsequentcycling occurred at 2 C.

Example 7

In a further example, the cells were also constructed to form themetallic lithium anode in-situ on the first charge cycle of the cell.The cells are cycled at room temperature and a rate of 1 C on charge and3 C discharge. Significantly, the cells retain more than 60% of theiroriginal capacity after 100 cycles in stark contrast to expectationbased on previous reports and the known literature. The capacity plotFIG. 9 shows the capacity fade as a function of the first 100 cyclesbased upon the normalized specific capacity of the lithium nickelmanganese oxide cathode active material. The as assembled constructionis lithium nickel manganese oxide cathode vs. Cu negative electrodesubstrate. As in FIG. 3, high purity Li metal electrodeposits at thenegative electrode substrate upon initial charging. The cycling wasconducted at room temperature and the C-rates depicted forcharge:discharge are 1 C:3 C. The capacity retention is greater than 60%over 100 cycles.

According to principles of the present invention, in some embodimentsthe operating voltage of the anode (negative electrode) is held at 1volt or less with respect the plating potential of a metal (examples areMg, Li) using the absolute electrochemical scale.

The N/P ratio in different embodiments of the present invention can bein a range selected from the ranges of zero to 0.10, zero to 0.20, zeroto 0.30, zero to 0.40, zero to 0.50, zero to 0.60, zero to 0.70, zero to0.80, zero to 0.85, zero to 0.90, 0.05 to 0.10, 0.05 to 0.20, 0.05 to0.30, 0.05 to 0.40, 0.05 to 0.50, 0.05 to 0.60, 0.05 to 0.70, 0.05 to0.80, 0.05 to 0.85, and 0.05 to 0.90.

Materials of Construction

We now provide example fluid electrolytes that are expected to besuitable for secondary battery systems containing N/P ratio<0.9. Inparticular, materials contemplated for use in the electrolytes of theinvention can be described by the general formula Me_(y)X_(z), where Meis an electroactive metal cation of the secondary cell and X is apolyatomic monovalent negative ion. Examples of X polyatomic monovalentanions that are believed to be useful in practicing the inventioninclude, but are not limited to, those described in Table I, andmixtures thereof. In some preferred embodiments Me is Mg, Li, or Nacation or mixtures thereof

TABLE I Chemical name Acronym Formula bis(perfluoroalkylsulfonyl)imidesN((CxF_(2x+1))_(x)SO₂)₂ ⁻¹ bis(fluorosulfonyl)imide FSI (x = 0) N(SO₂F)₂⁻¹ bis(trifluoromethanesulfonyl)imide TFSI (x = 1) N(CF₃SO₂)₂ ⁻¹bis(perfluoroethylsulfonyl)imide BETI (x = 2) N(C₂F₅SO₂)₂ ⁻¹ DicyanamideDCA N(CN)₂ ⁻¹ Tricyanomethide TCM C(CN)₃ ⁻¹ tetracyanoborate TCB B(CN)₄⁻¹ 2,2,2,-trifluoro-N- N(CF₃SO₂) (trifluoromethylsulfonyl)acetamide(CF₃CO)⁻¹ tetrafluoroborate BF₄ ⁻¹ hexafluorophosphate PF₆ ⁻¹ triflateCF₃SO₃ ⁻¹ bis(oxalato)borate BOB B(C₂O₄)₂ ⁻¹ difluoro(oxalato)borateDFOB BF₂(C₂O₄)⁻¹ perchlorate ClO₄ ⁻¹ hexafluoroarsenate AsF₆ ⁻¹Hexafluoroantimonate SbF₆ ⁻¹ Perfluorobutylsulfonate (C₄F₉SO₃)⁻¹Tris(trifluoromethanesulfonyl)methide C(CF₃SO₂)₃ ⁻¹ trifluoroacetateCF₃CO₂ ⁻¹ heptafluorobutanoate C₃F₇CO₂ ⁻¹ thiocyanate SCN⁻¹ triflinateCF₃SO₂ ⁻¹

A variety of organic solvents are suitable for use in the electrolyte ofthe present invention. The organic solvents can be used alone or incombination. Whether a solvent comprises a single organic composition ora plurality of organic compositions, for the purposes of furtherexposition, the organic solvent will be referred to as “the solvent” inthe singular. In order to provide for the reversible dissolution andplating of an electroactive metal, the solvent advantageously shouldprovide appreciable solubility by coordination of the constituentinorganic salts of the electroactive metal. In various embodiments,suitable solvents include ethers, organic carbonates, and tertiaryamines, and may also include, lactones, ketones, glymes, nitriles, ionicliquids, aliphatic and aromatic hydrocarbon solvents and organic nitrosolvents. More specifically, suitable solvents include THF, 2-methylTHF, dimethoxyethane, diglyme, triglyme, tetraglyme, diethoxyethane,diethylether, proglyme, ethyl diglyme, butyl diglyme, ethylenecarbonate, dimethyl carbonate, diethyl carbonate, dimethylsulfoxide,dimethylsulfite, sulfolane, ethyl methyl sulfone, acetonitrile, hexane,toluene, nitromethane, 1-3 dioxalane, 1-3 dioxane, 1-4 dioxane,trimethyl phosphate, tri-ethyl phosphate, hexa-methyl-phosphoramide(HMPA),N,N-propyl-methyl-pyrrolidinium-bis(trifluoromethylsulfonyl)imide(P13-TFSI), N,N-propyl-methyl-pyrrolidinium-diacetamide (P13-DCA),propyl-methyl-pyrrolidinium-bis(fluorosulfonyl)imide (P13-FSI),ethyl-dimethyl-propyl-ammonium-bis(trifluoromethylsulfonyl)imide(PDEA-TFSI), and1-(methoxyethyl)-1-methylpiperidinium-bis(trifluoromethylsulfonyl)imide(MOEMPP-TFSI).

Intercalation cathodes used in conjunction with the electrolyteaccording to the present invention preferably include transition metaloxides, transition metal oxo-anions, chalcogenides, and halogenides andcombinations thereof. Non-limiting examples of positive electrode activematerial for the Mg battery include Chevrel phase Mo₆S₈, MnO₂, CuS,Cu₂S, Ag₂S, CrS₂, VOPO₄, layered structure compounds such as TiS₂, V₂O₅,MgVO₃, MoS₂, MgV₂O₅, MoO₃, Spinel structured compounds such as CuCr₂S₄,MgCr₂S₄, MgMn₂O₄, MgNiMnO₄, Mg₂MnO₄, NASICON structured compounds suchas MgFe₂(PO₄)₃ and MgV₂(PO₄)₃, Olivine structured compounds such asMgMnSiO₄ and MgFe₂(PO₄)₂, Tavorite structured compounds such asMg_(0.5)VPO₄F, pyrophosphates such as TiP₂O₇ and VP₂O₇, and fluoridessuch as MgMnF₄ and FeF₃. Non-limiting examples of positive electrodeactive materials for the Li battery include Lithium transition metaloxides comprised of one or more transition metals and one or more redoxactive transition metals such as Lithium Cobalt Oxide, Lithium NickelManganese Cobalt Oxide compositions, Lithium Nickel Cobalt Aluminumcompositions. Non-limiting examples of positive electrode activematerials for the Li battery include Lithium metal phosphates andtavorites such as LiFePO4, Lithium metal oxide spinels LiMn2O4, and LiNASICON's Li3V2(PO4)3.

In some embodiments, the positive electrode layer further comprises anelectronically conductive additive. Non-limiting examples ofelectronically conductive additives include carbon black, Super P®,C-NERGY™ Super C65, Ensaco® black, Ketjenblack®, acetylene black,synthetic graphite such as Timrex® SFG-6, Timrex® SFG-15, Timrex®SFG-44, Timrex® KS-6, Timrex® KS-15, Timrex® KS-44, natural flakegraphite, carbon nanotubes, fullerenes, hard carbon, or mesocarbonmicrobeads.

In some embodiments, the positive electrode layer further comprises apolymer binder. Non-limiting examples of polymer binders includepoly-vinylidene fluoride (PVdF), poly(vinylidenefluoride-co-hexafluoropropene) (PVdF-HFP), Polytetrafluoroethylene(PTFE), Kynar Flex® 2801, Kynar® Powerflex LBG, and Kynar® HSV 900, orTeflon®.

Negative electrodes used in conjunction with the present inventioncomprise a negative electrode active material that can accept Mg-ions.Non-limiting examples of negative electrode active material for the Mgbattery include Mg, Mg alloys. Magnesium alloys names are often given bytwo letters following by two numbers. Letters tell main alloyingelements (e.g., A=aluminum, Z=zinc, M=manganese, S=silicon, K=zirconium,C=copper). Numbers indicate respective nominal compositions of mainalloying elements. Marking AZ91 for example conveys magnesium alloy withroughly 9 weight percent aluminum and 1 weight percent zinc. Suitablealloys include those such as AZ31, AZ61, AZ63, AZ80, AZ81, AZ91, AM50,AM60, ZK51, ZK60, ZK61, ZC63, M1A, ZC71, Elektron® 21, Elektron® 675,Elektron®, Magnox (e.g., Magnesium non-oxidizing). Other suitablechoices are insertion materials such as Anatase TiO₂, rutile TiO₂,Mo₆S₈, FeS₂, TiS₂, and MoS₂. Non-limiting examples of negative electrodeactive material for the Li battery Li, Li alloys such as Si, Sn, Bi, Al,Li4Ti5O12, hard carbon, graphitic carbon, amorphous carbon.

In some embodiments, the negative electrode layer further comprises anelectronically conductive additive. Non-limiting examples ofelectronically conductive additives include carbon black, Super P®,C-NERGY™ Super C65, Ensaco® black, Ketjenblack®, acetylene black,synthetic graphite such as Timrex® SFG-6, Timrex® SFG-15, Timrex®SFG-44, Timrex® KS-6, Timrex® KS-15, Timrex® KS-44, natural flakegraphite, carbon nanotubes, fullerenes, hard carbon, or mesocarbonmicrobeads.

In some embodiments, the negative electrode layer further comprises apolymer binder. Non-limiting examples of polymer binders includepoly-vinylidene fluoride (PVdF), poly(vinylidenefluoride-co-hexafluoropropene) (PVdF-HFP), Polytetrafluoroethylene(PTFE), Kynar Flex® 2801, Kynar® Powerflex LBG, and Kynar® HSV 900, orTeflon®.

In some embodiments, the Mg, Li, or Na metal anode battery used inconjunction with the electrolyte described herein comprises a positiveelectrode current collector comprising carbonaceous material, or acurrent collector comprising a metal substrate coated with an over-layerto prevent corrosion in the electrolyte. In some embodiments, the Mg,Li, or Na battery described herein comprises a negative electrodecurrent collector comprising any material capable of sufficientlyconducting electrons. In other embodiments, the Mg, Li, or Na batterydescribed herein comprises positive and negative electrode currentcollectors comprising any material capable of sufficiently conductingelectrons.

In some embodiments, the Mg, Li, or Na battery disclosed herein is abutton or coin cell battery comprising a stack of negative electrode,porous polypropylene or glass fiber separator, and positive electrodedisks sit in a can base onto which the can lid is crimped. In otherembodiments, the Mg, Li, or Na battery used in conjunction with theelectrolyte disclosed herein is a stacked cell battery. In otherembodiments, the Mg, Li, or Na battery disclosed herein is a prismatic,or pouch, cell comprising one or more stacks of negative electrode,porous polypropylene or glass fiber separator, and positive electrodesandwiched between current collectors wherein one or both currentcollectors comprise carbonaceous materials, or a metal substrate coatedwith an over-layer to prevent corrosion in the electrolyte. The stack(s)are folded within a polymer coated aluminum foil pouch, vacuum and heatdried, filled with electrolyte, and vacuum and heat sealed. In otherembodiments, the Mg, Li, or Na battery disclosed herein is a prismatic,or pouch, bi-cell comprising one or more stacks of a positive electrodewhich is coated with active material on both sides and wrapped in porouspolypropylene or glass fiber separator, and a negative electrode foldedaround the positive electrode wherein one or both current collectorscomprise carbonaceous materials. The stack(s) are folded within apolymer coated aluminum foil pouch, dried under heat and/or vacuum,filled with electrolyte, and vacuum and heat sealed. In some embodimentsof the prismatic or pouch cells used in conjunction with the electrolytedescribed herein, an additional tab composed of a metal foil orcarbonaceous material of the same kind as current collectors describedherein, is affixed to the current collector by laser or ultrasonicwelding, adhesive, or mechanical contact, in order to connect theelectrodes to the device outside the packaging.

In other embodiments, the Mg, Li, or Na battery used in conjunction withthe electrolyte disclosed herein is a wound or cylindrical cellcomprising wound layers of one or more stacks of a positive electrodewhich is coated with active material on one or both sides, sandwichedbetween layers of porous polypropylene or glass fiber separator, and anegative electrode wherein one or both current collectors comprisecarbonaceous materials. The stack(s) are wound into cylindrical roll,inserted into the can, dried under heat and/or vacuum, filled withelectrolyte, and vacuum and welded shut. In some embodiments of thecylindrical cells described herein, an additional tab composed of ametal foil or conducting material of the same kind as current collectorsdescribed herein, is affixed to the current collector by laser orultrasonic welding, adhesive, or mechanical contact, in order to connectthe electrodes to an external circuit outside the packaging.

DEFINITIONS

Unless otherwise explicitly recited herein, any reference to “secondary”or “rechargeable” cell is understood to refer to an electrochemical cellcapable of undergoing repeated charge and discharge.

Unless otherwise explicitly recited herein, any reference to “capacity”is understood to refer to amp-hours provided by the cell or device undernormal operating conditions.

Unless otherwise explicitly recited herein, any reference to“non-aqueous fluid electrolyte” is understood to refer to a non-aqueousliquid electrolyte or a non-aqueous gel electrolyte, and not to a moltensalt electrolyte.

Unless otherwise explicitly recited herein, any reference to “currentcollector” is understood to refer to any material capable ofsufficiently conducting electrons.

Unless otherwise explicitly recited herein, any reference to anelectronic signal or an electromagnetic signal (or their equivalents) isto be understood as referring to a non-volatile electronic signal or anon-volatile electromagnetic signal.

Unless otherwise explicitly recited herein, any reference to “record” or“recording” is understood to refer to a non-volatile or non-transitoryrecord or a non-volatile or non-transitory recording.

Recording the results from an operation or data acquisition, forexample, recording results such as an electrical signal having aparticular frequency or wavelength, or recording an image or a portionthereof, is understood to mean and is defined herein as writing outputdata in a non-volatile or non-transitory manner to a storage element, toa machine-readable storage medium, or to a storage device. Non-volatileor non-transitory machine-readable storage media that can be used in theinvention include electronic, magnetic and/or optical storage media,such as magnetic floppy disks and hard disks; a DVD drive, a CD drivethat in some embodiments can employ DVD disks, any of CD-ROM disks(i.e., read-only optical storage disks), CD-R disks (i.e., write-once,read-many optical storage disks), and CD-RW disks (i.e., rewriteableoptical storage disks); and electronic storage media, such as RAM, ROM,EPROM, Compact Flash cards, PCMCIA cards, or alternatively SD or SDIOmemory; and the electronic components (e.g., floppy disk drive, DVDdrive, CD/CD-R/CD-RW drive, or Compact Flash/PCMCIA/SD adapter) thataccommodate and read from and/or write to the storage media.

Theoretical Discussion

Although the theoretical description given herein is thought to becorrect, the operation of the devices described and claimed herein doesnot depend upon the accuracy or validity of the theoretical description.That is, later theoretical developments that may explain the observedresults on a basis different from the theory presented herein will notdetract from the inventions described herein.

Any patent, patent application, patent application publication, journalarticle, book, published paper, or other publicly available materialidentified in the specification is hereby incorporated by referenceherein in its entirety. Any material, or portion thereof, that is saidto be incorporated by reference herein, but which conflicts withexisting definitions, statements, or other disclosure materialexplicitly set forth herein is only incorporated to the extent that noconflict arises between that incorporated material and the presentdisclosure material. In the event of a conflict, the conflict is to beresolved in favor of the present disclosure as the preferred disclosure.

While the present invention has been particularly shown and describedwith reference to the preferred mode as illustrated in the drawing, itwill be understood by one skilled in the art that various changes indetail may be affected therein without departing from the spirit andscope of the invention as defined by the claims.

What is claimed is:
 1. A rechargeable electrochemical storage device,comprising: an anode electrode comprising the metal form of theelectro-active species, said rechargeable electrochemical storage deviceconfigured to electroplate metal at said anode electrode, said anodeelectrode comprising N/P<4 of electro-active material in the dischargedstate.
 2. The rechargeable electrochemical storage device of claim 1,configured to charge to greater than or equal to 4.0 V.
 3. Therechargeable electrochemical storage device of claim 1, configured todischarge to −2.5 V.
 4. The rechargeable electrochemical storage deviceof claim 1, configured to charge and discharge at ≦10 C-rate of ratedcapacity.
 5. The rechargeable electrochemical storage device of claim 1,configured to discharge and charge at temperatures in the range of −20°C. and 200° C.
 6. The rechargeable electrochemical storage device ofclaim 1, configured to charge and discharge with >99.35% Coulombicefficiency.
 7. The rechargeable electrochemical storage device of claim1, configured to provide at least 80% of initial capacity for greaterthan 30 charging and discharging cycles.
 8. The rechargeableelectrochemical storage device of claim 1, wherein said negativeelectrode is configured to provide>1000 mAh/cc.
 9. The rechargeableelectrochemical storage device of claim 1, wherein said non-aqueousfluid electrolyte comprises at least one active cation selected from thegroup consisting of Mg ion, Al ion, Ca ion, Sr ion, Ba ion, Li ion, Naion, K ion, Rb ion, Cs ion, and onium.
 10. The rechargeableelectrochemical storage device of claim 1, wherein said non-aqueousfluid electrolyte contains a symmetric or asymmetric aluminum-based orboron-based anion.
 11. The rechargeable electrochemical storage deviceof claim 1, wherein said non-aqueous fluid electrolyte comprises a salt,or combination of salts in a concentration in the range of 0.5 M tosaturated concentration.
 12. The rechargeable electrochemical storagedevice of claim 1, wherein a pressure perpendicular to the interface ofthe positive and negative electrodes is greater than 0.06 MPa.
 13. Therechargeable electrochemical storage device of claim 1, furthercomprising at least one gate electrode having a gate electrodeelectrical terminal, said gate electrode in communication with saidnon-aqueous fluid electrolyte and permeable to at least one mobilespecies which is redox-active at at least one of said positive electrodeand said negative electrode, said gate electrode situated between saidpositive electrode and said negative electrode.
 14. The rechargeableelectrochemical storage device of claim 1, comprising a metal which isconfigured to plate onto said negative electrode during charging. 15.The rechargeable electrochemical storage device of claim 1, wherein saidmetal is selected from the group consisting of Mg, Li, and Na.
 16. Therechargeable electrochemical storage device of claim 1, wherein a ratiodefined by said capacity of said negative electrode divided by saidcapacity of said positive electrode is in a range selected from theranges of zero to 0.40, zero to 0.80, zero to 1.2, zero to 1.6, zero to2.0, zero to 2.4, zero to 2.8, zero to 3.2, and zero to
 4. 17. Therechargeable electrochemical storage device of claim 1, wherein a ratiodefined by said capacity of said negative electrode divided by saidcapacity of said positive electrode is in a range selected from theranges of 0.20 to 0.40, 0.20 to 0.80, 0.20 to 1.2, 0.20 to 1.6, 0.20 to2.0, 0.20 to 2.4, 0.20 to 2.8, 0.20 to 3.2, and 0.20 to 4.